Fluid jet amplifier



Jan. 7, 1969 United States Patent O 3,420,253 FLUD JET AMPLIFER WilliamS. Griffin, Lakewood, Ohio, assigner to the United States of America asrepresented by the administrator of the National Aeronautics and SpaceAdministration Filed .lune 9, 1965, Ser. No. 462,762

ABSTRACT F THE DISCLOSURE A fiuid amplifier including a jet, aninteraction region and a receiver. Vent means are provided for theinteraction region. Receiver outlets are connected to the interactionregion through a receiver intermediate passageway and a receiver inletpassageway which are out of alignment with one another. A ventpassageway which is in alignment with the receiver intermediatepassageway is provided to receive reverse fiuid flow from the receiver.

The invention described herein was made by an employee of the UnitedStates Government and may lbe manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

The instant invention relates to fluid systems. More particularly, theinstant invention relates to an improved fluid jet amplifier.

A fluid jet amplifier as described herein is a no moving parts devicewhich is capable of amplifying fluid signal fiows and pressures in muchthe same manner as its electrical equivalent, the transistor, amplifiescurrents and voltages. A tiuid jet amplifier can utilize either aliquid, a gas, or a combination thereof.

Basically, a iiuid jet amplifier is a device wherein an input fiuidfiowing through a nozzle forms a jet which is caused to iiow through aninteraction region or cavity wherein the jet may be defiected to oneside or another of said region by means of pressures developed in theinteraction region by the iiow fluids established therein and/or the useof control signals or nozzles located on either side of the jet.Introducing fiow at one of the control nozzles causes the cavitypressure on that side of the jet to be raised thus causing the jet todeiiect to the other side. Effectively capturing and utilizing theoutput flow from the iiuid jet amplifier is much more diicult thanloading a transistor. The usual method consists of placing a pair ofreceivers immediately downstream of the interaction or cavity region.

In fluid jet amplifiers of the type described herein various problemshave been encountered which can greatly effect its performance.

One problem involves the furnishing of a fiow restriction lbetween thecontrol line and the cavities of the interaction region of a bistableamplifier. For a Coanda effect iiuid jet amplifier to be bistable inoperation, some type of restriction must be provided. One methodconsists of placing an oril'ice restriction in the control lines leadingto the interaction region. The volume in the control signal linesbetween the orifice restriction and the interaction region can be largein comparison to the volume of the cavities in the interaction region,can reduce switching speeds and cause transient instabilities to occurduring switching. It has also been proposed to form the proper orificerestriction by having a control port of narrow width located in closeproximity to the side wall of the main jet. However, for the amplifierto have high triggering sensitivity, the sidewalls must be set back fromthe main power nozzle a small and precisely controlled amount. Inasmuchas the performance of the amplifier is quite 3,420,253 Patented Jan. 7,1969 ICC sensitive to the amount of the sidewall setback, smallmanufacturing errors can cause variations in the amplifier performance.Furthermore, a fairly large control signal flow may be demanded even inthe absence of a control pressure signal. This quiescent control flowmust be taken into account in the design of fluid jet amplifiers.Failure to take this control fiow into account can result in inadvertentswitching of the amplifier.

Another problem is that the reverse fiow exiting from one of thereceiver channels toward the interaction region can cause a change inthe amplifiers performance. Such a situation is likely to occur if thereceivers are connected to a moving piston or if they are connected to alarge volume and the jet is suddenly switched from one side to another.Also, lblockage or restriction of the receiver output fiow can sometimescause unstable operation. It has been proposed to put a plurality ofbleeds in the load. However, this can cause great losses in power. Otherproposed solutions include putting a cusp on the splitter in order tocreate a stabilizing vortex and drilling a hole in the receiver channelat a right angle to the plane of the amplifier. However, this lattermethod will also cause low power recovery.

It is therefore an object of the instant invention to reduce thesensitivity of a fiuid amplifier to receiver reverse flow.

It is another object of the instant invention to provide for a fluidamplifier that is stable under all load conditions.

It is still another object of the instant invention to provide for animproved duid amplifier that will maintain good pressure and flowrecoveries and at the same time be stable under all load conditions.

It is still another object of the instant invention to provide for animproved fluid amplifier wherein the receiver reverse ow is preventedfrom changing the control pressure and fiow required to switch saidamplifier.

It is yet still another object of the instant invention to eliminateusing large safety factors in computation of control pressures and flowsin fiuid amplifiers.

It is another object or" the instant invention to provide for a fluidamplifier that can be used with a piston type load.

It is another object of the instant invention to reduce the control flowrequired in the absence of controlled pressure signal in a fiuidamplifier.

It is still another object of the instant invention to provide a fiuidjet amplifier which requires low control signal pressures and fiows andwhich `does not require a small, precisely controlled wall offset at thebeginning of the interaction region.

It is another object of the instant invention to provide for a tiuidamplifier having large deflection angles and a short interaction regionlength.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed ydescription when considered inconnection with the accompanying drawings in which like referencenumerals designate like parts throughout the figures thereof and whereinFIG. l is a schematic elevational section view of one embodiment of theinstant invention and FG. 2 is an enlarged view of the portion of thedevice shown in FIG. 1 enclosed within the dotted line.

In accordance with this invention the aforesaid and other objects areachieved by `designing a fiuid amplifier wherein an effective orificerestriction is formed by the edge of the control port with the main jetstream. The control ports or nozzles are located upstream from theinteraction region. In addition, the receiver channels are designed sothat the mouth of the channels are displaced laterally and pointing awayfrom the interaction region.

The receiver section of the amplier is further provided with a bafflewall to separate the receiver reverse flow from the entrainment ow tothe interaction region of the iiuid jet ampliiier.

Referring now to the drawings wherein like reference numerals representlike parts there is shown in FIGS. 1 and 2 a uid amplifier comprising asubstantially solid body 10. iIn the embodiment shown the solid body isfabricated from a transparent plastic. However, any other suitablematerial possessing suitable `strength Such as ceramics, opaqueplastics, or metals may also be employed. The solid body 10 is providedwith a plurality of channels or passage ways through which a fluid mayflow. These passageways are either cut, etched or otherwise suitablyformed therein. The completed fluid amplifier also includes a coverplate (not shown) which may be fabricated from any of theabove-mentioned materials. The cover plate is fastened in a Huid-tightrelationship to the solid body by means of screws (also not shown).However, any other type of sealing means such as cement may be employed.In FIG. l the holes 21 for receiving the screws or other similarfasteners are shown suitably spaced about the solid body.

The solid body member 10 is comprised basically of three parts. Namely apower and control inlet section, van interaction region, and a receiversection.

The power and control inlet section includes a primary fluid supply port31 through which a compressor or pump (not shown) supplies a suitableregulated stream of uid into ra primary uid input chamber 32. Aplurality of guide vanes 33 in the form of projections are locatedwithin the iiuid input chamber 32 to aid in directing and smoothing thestream of fluid into a power nozzle 34.

A pair of secondary uid supply ports 41, 42 are located on either sideof the main power nozzle 34. These secondary ports 41, 42 introducecontrol signal pressures and flows into their respective connectingcontrol port channels 43, `44. The control port channels 43, 44 in turnconnect respectively to .a pair of control inlets 45, 46 positionedadjacent to the main power nozzle 34 and the main power stream. Saidcontrol inlets 45, 46 introduce control ow into the interaction regionthrough an orifice restriction I51 formed by the edge of the controlinlets 45, 46 land the main jet power stream. The walls of the orificesrestriction 52, 53 are in substantial align-ment with the walls of themain power nozzle 34. The length of the orifice restriction l51 is sizedso as to be either equal to or less than one half the width of the mainpower nozzle 34. This method of providing an orifice restriction enablescontrol flow to be introduced into an interaction region with only asmall control pressure and reduces the quiescent control iiow demandedby the interaction region when no control pressure is present. Theinteraction region or section includes an interaction region chamber 61.As shown in FIGS. 1 and 2 the interaction region chamber 61 is formed bya plurality of sidewalls 62, 63, 64, 65 and a pair of interaction regionbackwalls 66, 67. Interaction region sidewalls 62, 63 are bent at anangle equal to the angular deiiection of the main power jet. A pair ofinteraction region vents 71, 72 are in communication with theinteraction region chamber `61 and furnish entrainment ow at ambientpressure to the interaction region. These interaction region vents 71,72 in turn exit by means of a pair of interaction region vent ports 73,74 connected to exhaust pressure.

A receiver section or portion is located immediately downstream of theinteraction chamber. The receiver portion includes a pointed dividermember 81 located immediately downstream of the interaction regionchamber 61. The divider member 81 includes a centrally disposed an axissubstantially parallel to the interaction region sidewalls 62, 63. Thereceiver connecting inlet passages 84, 85 in turn exit into a pair ofreceiver intermediate passage ways 86, 87 at a shallow angle (20 in FIG.1). The receiver intermediate passages, 86, 87 are displaced laterallyfrom the interaction region 61 and angled such that yany reverse flowfrom them will completely miss the interaction region 61. Because thereverse flow completely misses the interaction region 61, changes ininteraction region performance as -a result of receiver reverse ow arereduced. By means of this angle between the receiver connecting inletpassages 84, 85 and the receiver intermediate passages 86, 87, anyreceiver reverse ow can be directed away from the interaction region 61.

To further prevent any receiver reverse flow from either returning tothe interaction region chamber 61 `or interfering with entrainment iowto the interaction region 61, a pair of receiver vents 91, 92 arelocated on either side of the receiver connecting inlet passages 84, 85.The receiver vents 91, 92 are in the form of channels which are insubstantial alignment with the reeciver intermediate passage ways andwhich terminate in receiver vent ports 93, 94. Each area bounded by areceiver vent 91, 92, its adjacent receiver connecting inlet passage 84,`85 and its adjacent interaction region vent 71, 72 forms a baie wall95, 96. By means of the receiver Vent 91, 92 in cooperation with thebafe wall 95, 96, any receiver reverse iiow will be prevented fromtravelling down into the receiver connecting inlet passageways 84, 85 orinterfering with entrainment flow delivered to the interaction region.This flow pattern is shown schematically by arrows in the channels 'ofFIG. 1. The receiver intermediate passageways 86, 87 in turn exit into apair of diffuser sections 88, 89 lwhich in turn exit into a plurality ofreceiver outlets 101, 102, 103, 104, 105, 106 which may be connectedinto a plurality of arbitrarily chosen loads, such as the control portsof other iiuid jet ampliers, Volumes, pistons, bellows, or positivedisplacement motors.

An amplifier according to the instant invention has been built andtested. Execellent results were obtained with the following power nozzle(34), interaction region (61) land receiver dimensions:

Power nozzle width 31--D5 Spacing between interaction sidewalls 64,65-2.2Dj

Length `of interaction region sidewalls 6-4, 65-2.2DJ

Length of exit portion of interaction region sidewalls Angle of receiverinlet passages 84, 85-20" Width of center vent port Y83-.813DJ Width ofreceiver inlet passages 84, 85-1.3Dj

Width of receiver intermediate passages 86, 87-1.3Dj

Width of interaction region vents 71, 72-J813D3 Width of control ports45, 46-.813DJ With an amplifier of the above-listed specifications,average control pressures and flows of 7 pecrent and 5 percent of supplypressures and flows, respectively, were required to switch the powerjet. Increasing the control pressure by 60 percent enabled the power jetto be switched into a reverse iiowing receiver pressurized at 40 percentof the supply pressure to the main power noLzle 31.

The yaforesaid performance gures were obtained with an amplier having athroat width of .040 and a supply pressure of 1.0 p.s.i.g. The limits onrange of pressures were determined by a maximum throat Mach number of .8and a minimum throat Reynolds number (based on throat width, Dj) of4000. The ratio of depth of the amplitiers channels to throat width was1.5.

Obviously many modifications and Variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood, that within means in communication with the power inletmeans for controllably deliecting said stream of uid under pressure, anorifice restriction in communication with the power inlet means andlocated downstream of the control inlet means, an interaction chamber incommunication with the oriiice restriction and located downstream fromsaid oriiice restriction, interaction region vent means in communicationwith the interaction region chamber for furnishing entrainment flow tosaid interaction chamber and receiver means positioned downstream of theinteraction chamber, said receiver means including receiver vent meansfor providing a path thereby for receiver reverse flow.

2. The invention according to claim 1 wherein said power inlet meansincludes a power nozzle and wherein said orifice restriction is insubstantial alignment with said power nozzle.

3. The invention according to claim 2 wherein the length of the oriiicerestriction is one-half the width of the main power nozzle.

4, The invention according to claim 1 wherein said receiver meansincludes a receiver connecting inlet passage way in communication withthe interaction chamber downstream of the interaction region vent meansand an intermediate passage way for connecting the receiver inletpassage Way into a receiver outlet, said receiver inlet passage waybeing out of alignment with the receiver intermediate passage way andsaid receiver vent being in alignment with the receiver intermediatepassage way.

5. The invention according to claim 4 wherein said receiver inletpassage way intersects the receiver intermediate passage way at an angleof approximately 20 degrees and wherein said receiver vent passage wayand said receiver intermediate passage way form an angle ofapproximately 180 degrees.

References Cited UNITED STATES PATENTS 3,122,165 2/1964 Horton 137-8153,187,763 6/1965 Adams 137-815 3,209,775 10/1965 Dexter et al 137-8153,225,780 12/1965 Warren et al 137-815 3,261,372 7/1966 Burton 137-8153,269,419 8/1966 Dexter 137-815 3,270,758 9/1966 Bauer 137-815 3,282,28111/1966 Reader 137-815 FOREIGN PATENTS 1,329,569 5/ 1963 France.

SAMUEL SCOTT, Primary Examiner.

